1. Field of the Invention
This invention relates to an element, preferably photographic element, containing at least two contiguous gelatin-containing layers wherein reticulation is reduced.
2. State of the Art
The use of gelatin, a hydrophilic colloid, as the binding agent or vehicle in photographic silver halide emulsions and elements is well known. Attempts have been made to substitute various synthetic and natural materials for all or a part of the gelatin to improve certain photographic and physical properties.
However, improvement in one property is generally achieved at the expense of another and often more important property. For example, substitution of part of the gelatin with at least one other hydrophilic colloid as the vehicle or binding agent in a silver halide emulsion layer increases the covering power, thus yielding a higher density upon development for the same amount of silver per unit area. This often reduces layer mechanical strength.
Such layers do not have good abrasion resistance and must therefore usually be coated with an overcoat layer. It has been found that overcoat layers, containing gelatin and mixtures of gelatin and other hydrophilic colloids are suitable for this purpose. The addition of certain materials to both the silver halide layer and the overcoat layer improves resistance to abrasion, particularly when processed in high speed automatic processing equipment such as described in U.S. Pat. No. 3,147,090 and 3,025,779. This equipment is particularly important, for example, in hospitals where rapid access to emergency x-ray photographs are desired in emergency situations and in high volume. The use of high-speed, high-temperature processing operations, however, results in a reticulation problem in the photographic element. The gelatin-containing overcoat layer swells at a different rate than the gelatin-containing silver halide layer which results in layer buckling.
The use of fillers containing gelatin hardeners to reduce overcoat layer lateral swell, does reduce the tendency of the element to reticulate. The addition of diffusible hardeners in the overcoat layer which migrate to the silver halide layer aids in reducing reticulation but also reduces sensitivity of the element. Examples of the use of these gelatin hardeners are found in U.S. Pat. Nos. 3,926,869 and 4,172,732.
Non-diffusible hardeners have not been used in the overcoat layer, as these hardeners are known to increase reticulation as described in "Reticulation in Gelatin Layers" by E. Tojo et al in Photographic Gelatin, R. J. Cox, Editor, Academic Press, 1972.
It is highly desirable to provide an element comprising two contiguous gelatin-containing layers containing an additive which reduces reticulation without adversely affecting other properties of the element to allow the use of high-speed coating operations.